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From: "christophm30 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/105314] [12 Regression] ifcvt regression in noce_try_store_flag_mask
Date: Mon, 25 Apr 2022 22:40:17 +0000	[thread overview]
Message-ID: <bug-105314-4-qWjlT2blsN@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-105314-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105314

--- Comment #6 from Christoph Müllner <christophm30 at gmail dot com> ---
The proposed fix is triggering an invalid transformation.

The pattern we need to transform is:
  Convert "if (test) x = 0;" to "x &= -(test == 0);"

If there is an else branch, we can't apply the transformation.

Error case:
"""
long func2 (long a, long b, long c)  // should not be optimized
{
    if (c)
        a = 0;
    else
        a = 5;
    return a;
}
"""

With the patch this gets compiled to:
0000000000000006 <func2>:
   6:   00163513                seqz    a0,a2
   a:   40a00533                neg     a0,a0
   e:   8915                    andi    a0,a0,5
  10:   8082                    ret

  parent reply	other threads:[~2022-04-25 22:40 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-19 20:19 [Bug tree-optimization/105314] New: " christophm30 at gmail dot com
2022-04-19 20:23 ` [Bug tree-optimization/105314] " christophm30 at gmail dot com
2022-04-20  7:10 ` marxin at gcc dot gnu.org
2022-04-20  7:10 ` marxin at gcc dot gnu.org
2022-04-20  7:49 ` [Bug target/105314] " rguenth at gcc dot gnu.org
2022-04-22  9:48 ` [Bug target/105314] [12 Regression] " pinskia at gcc dot gnu.org
2022-04-25 15:45 ` [Bug rtl-optimization/105314] " jakub at gcc dot gnu.org
2022-04-25 22:34 ` ptomsich at gcc dot gnu.org
2022-04-25 22:40 ` christophm30 at gmail dot com [this message]
2022-04-25 22:47 ` ptomsich at gcc dot gnu.org
2022-04-26  0:05 ` christophm30 at gmail dot com
2022-04-26  8:12 ` cvs-commit at gcc dot gnu.org
2022-04-26  8:13 ` jakub at gcc dot gnu.org
2024-01-26 21:48 ` cvs-commit at gcc dot gnu.org

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